PROJECT SUMMARY There are currently over 700,000 end stage renal disease (ESRD) patients in the United States. Approximately 70% of ESRD patients undergo hemodialysis as their primary kidney replacement therapy. An arteriovenous fistula (AVF) is the preferred type of vascular access in hemodialysis patients. However, nearly 60% of AVFs created develop AVF maturation failure due to early venous neointimal hyperplasia formation and impaired outward vascular remodeling. The pathological mechanisms underlying AVF maturation failure is poorly understood. Therefore, a major unmet clinical need in the field is the lack of effective therapies to treat and prevent AVF maturation failure. The central hypothesis of this study is that AVF creation will result in dysregulation of nitric oxide (NO) and cGMP activity that will disrupt proper AVF maturation by influencing AVF remodeling and neointimal hyperplasia formation. Therefore, NO/cGMP signaling pathway is an important therapeutic target for clinically successful AVF maturation. In order to study the role of NO and cGMP on AVF maturation we will 1) test the hypothesis that locally delivered NO therapy at the time of AVF creation will improve AVF maturation by inhibiting neointimal hyperplasia and enhance AVF remodeling, and reduce local inflammation; 2) test the hypothesis that a selective PDE5A inhibitor, which prevents cGMP degradation, administered before and after AVF creation, will improve AVF outward remodeling and inhibit neointimal hyperplasia; and will be also beneficial in the setting of chronic kidney disease (CKD), where AVFs are created in this clinical setting. These aims will be achieved using a rodent AVF model that has (1) an identical anatomic configuration to human AVF and (2) recapitulates the lesion of progressive venous neointimal hyperplasia seen in human AVF. Our studies are expected to elucidate the pathologic significance of NO/cGMP signaling pathway on AVF maturation as well as provide the basis to develop novel therapeutic strategies to treat and prevent AVF maturation failure in hemodialysis patients.